Feng (2004) suggested using the standard liquid limit cone but with smaller soil container as shown in Figure 7 to determine the plastic limit. The penetration depth of 2 mm is used as criteria to determine the plastic limit. The justification for the use of smaller container is due to the facts that the influence zone for a stiff soil is much less compare to the soft soil. Thus, a small specimen container with an inside diameter of 20 mm and a depth of 20 mm was designed to contain 6.3 cm3 of soil sample for cone penetration less than 1